Date Approved

2018

Degree Type

Open Access Senior Honors Thesis

Department or School

Biology

First Advisor

Kristin Judd

Second Advisor

Aaron Liepman

Third Advisor

Marianne Laporte

Abstract

Wetlands provide a number of important ecosystem services, but their anoxic conditions also favor the production of several greenhouse gases. Wetlands are an ideal environment for methanogenesis, the process by which carbon dioxide is reduced to methane by wetland microbes (methanogens). As wetlands are the largest natural contributor to the atmospheric methane pool, it is important to understand variables that control wetland methane production. Nitrogen availability is one variable that likely affects methanogen communities. Nitrate drains from agricultural areas, where wetlands act as a nitrogen sink, preventing nitrate from contaminating aquatic systems. Another factor that may affect wetland methanogenesis is vegetation type. In recent years, invasives such as exotic cattail (Typha angustifolia and Typha x glauca} and Phragmites have spread through wetlands, negatively impacting ecosystem processes. To determine the influence of nitrate availability and vegetation type on wetland methanogenesis, we incubated sediment from Phragmites and exotic cattail dominated stands, added increasing concentrations of nitrate, and measured methane production. We hypothesized that if nitrate allows methanogens to be outcompeted by another group of wetland microbes, denitrifiers, then we would observe decreased methane production with high nitrate concentrations.

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